Enhanced biogas production from anaerobic co-digestion of lignocellulosic biomass and poultry feces using source separated human urine as buffering agent

Effect of source separated human urine as buffering agent compared to sodium bicarbonate and water in anaerobic co-digestion of lignocellulosic biomass and poultry feces was evaluated in laboratory scale reactor for 180 days at 37 ± 2°C. Mean biogas volume ranged from 37 ± 8 to 101 ± 18 mL gVS−1 in the urine buffered reactors which was 1–5 times higher than the bicarbonate and water buffered reactors and the difference was significant at p = 0. 05. Total volatile fatty acids (VFA) concentration ranged between 396 and 1,400 mg L−1 with a pH of 6.9 ± 0.3 and 7.8 ± 0.1, respectively. In contrast, VFA concentration ranged between 386 and 3,109 mg L−1 (pH 7.6 ± 0.2 and 4.8 ± 0.4) in sodium bicarbonate buffered digestate and control (water) respectively. The result indicates buffering capacity of urine on anaerobic co-digestion with positive effect on biogas production. The Archaeal isoprenoids included markers of aceticlastic and hydrogenotrophic methanogens with a relative abundance that ranged between 0.71–18, 3–55, and 2–59 μg g−1 dry matter in the water (control), bicarbonate and urine buffered digestate, respectively. The Archaeal abundance was 1.12 and 6 times higher in the combined female/male urine than the bicarbonate buffered digestate and the control, and the difference was significant at p = 0.05. Overall, this study demonstrates that human urine with no pharmaceutical loadings as a wetting and buffering agent is a promising option for anaerobic co-digestion with competitive edge over sodium bicarbonate on lignocellulosic biomass saccharification for enhanced biogas production.